1.What kind of organ is the thyroid gland? The thyroid gland is the largest endocrine gland in the human body and is located in the neck under the thyroid cartilage immediately in front of the third and fourth cartilage ring of the trachea, consisting of two lobes and the isthmus forming an “H” shape, like a butterfly with open wings in front of the neck. The average weight of the thyroid gland is about 20-25g for adults, and slightly heavier for women. Behind the thyroid gland are four parathyroid glands and the recurrent laryngeal nerve. The main function of the thyroid gland is to synthesize and secrete thyroxine, which is regulated by thyroid stimulating hormone (TSH) secreted by pituitary cells; TSH is controlled by thyroid releasing hormone (TRH) secreted by the hypothalamus, thus forming The hypothalamic-pituitary-thyroid axis finely regulates the secretion of thyroid hormones by the thyroid gland. But on the other hand, the level of thyroid hormone in the blood also feeds back to the amount of TSH secreted by the pituitary gland. 2.What is thyroid hormone? What is its function? The thyroid hormone secreted by the thyroid gland is divided into two types: triiodothyronine (T3) and tetraiodothyronine (T4), most of which are T4. T3 has 5-10 times more binding power and biological activity than T4, but T3 is metabolized very quickly in the body and is a hormone with strong effects but short life span. This change is regulated by the body’s regulatory functions, as T4 is converted to T3 when there is sufficient energy and the conversion is suppressed when there is starvation. Thyroid hormones regulate the metabolic processes of the body. Insufficient thyroid hormone in childhood will cause intellectual and neurological developmental disorders, and in severe cases, mental retardation and dullness; thyroid hormone can increase the oxygen consumption and heat production of tissues and cells throughout the body, and promote the decomposition of protein, carbohydrate and fat to produce heat to maintain a constant body temperature. 3. What is the location and physiological role of the parathyroid glands? The parathyroid glands are small, flat, oval-shaped glands that are yellowish-brown in color, often located on both sides of the posterior wall of the thyroid gland, or buried in the thyroid tissue or in the mediastinum of the thoracic cavity. About 93.5% of people have two pairs, but there are also as many as five or only two. In normal people, each parathyroid gland contains 30 to 50 mg of blood and is approximately 6.5 mm x 3.5 mm x 1.5 mm. The gland has a rich blood supply and is composed of principal cells and eosinophils. The principal cells are rich in glycogen and are the cells that secrete parathyroid hormone (PTH). When secretion is active, the cytoplasm contains a large number of secretory granules. Eosinophils do not contain glycogen but eosinophilic granules, have a larger cytosol with an eosinophilic cytoplasmic staining process, do not secrete hormones, and are generally considered to be degenerated principal cells. The function of hormones secreted by parathyroid glands is to regulate calcium metabolism and maintain blood calcium balance, and insufficient secretion can cause a drop in blood calcium and hand-foot convulsions; when the function is hyperactive, it can cause excessive bone resorption and fracture easily, and prolonged hyperactivity can easily cause body shortening. Therefore, some people with the above symptoms should consider whether it is related to parathyroid dysfunction. 4.How to treat thyroglossal cysts? Is it related to the thyroid gland? A thyroglossal cyst is a congenital malformation related to the development of the thyroid gland. It mostly appears as a cystic mass in the anterior midline of the neck between the hyoid bone and the thyroid cartilage, and can move up and down with tongue extension or swallowing. The cyst may remain unchanged and asymptomatic for many years; however, if it is complicated by infection, redness, swelling, heat, pain and systemic infection symptoms may occur. Infected cysts can form fistulas that are difficult to heal when they rupture. Surgical excision of the fistula, the cyst wall and the middle 1/3 of the hyoid bone is appropriate for treatment. To rule out the possibility of ectopic thyroid, a preoperative thyroid nuclear scan or cervical thyroid ultrasound is required to avoid hypothyroidism after resection; in addition, enhanced CT of the neck helps to determine the adjoining of the cyst or fistula and helps in surgery. Surgery is usually elective and can be treated in patients over 2 years of age. If the cyst is located at the base of the tongue and presents with respiratory distress, it should be removed as early as possible. Recurrence is rare after surgical completion of the cyst wall and fistula.